<template>
  <div class="nav-bar" :class="{'is_fixed':isFixed}">
    <div class="container">
      <div class="pro-title">{{title}}</div>
      <div class="pro-params">
        <a href="javascript:;">概述</a>
        <span>|</span> 
        <a href="javascript:;">参数</a>
        <span>|</span>
        <a href="javascript:;">用户评价</a>
        <slot name="buy"></slot>
      </div>
    </div>
  </div>
</template>

<script>
export default {
  name: "nav-bar",
  props:{
    title:String
  },
  data(){
    return {
      isFixed:false
    }
  },
  // 监听滚动事件
  mounted(){
    window.addEventListener('scroll',this.initHeight)
  },
  methods:{
    // 滚动事件，当滚动到相应位置时，给nav-bar添加is_fixed类
    initHeight(){
      let scrollTop = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop
      this.isFixed = scrollTop > 152 ? true :false
    }
  },
  
  destroyed(){
    // 监听销毁滚动事件
    window.removeEventListener('scroll',this.initHeight,false)
  },
};
</script>

<style lang="scss">
@import "./../assets/scss/config.scss";
@import "./../assets/scss/mixin.scss";
.nav-bar {
  height: 70px;
  line-height: 70px;
  border-top: 1px solid $colorH;
  background-color: $colorG;
  z-index: 10;
  &.is_fixed{
    position: fixed;
    top: 0;
    width: 100%;
    box-shadow: 0 5px 5px $colorE;
  }
  .container {
    @include flex();
    .pro-title {
      font-size: $fontH;
      color: $colorB;
      font-weight: bold;
    }
    .pro-params{
      font-size: $fontJ;
      a{
        color: $colorC;
      }
      span{
        margin: 0 10px;
      }
    }
  }
}
</style>